
import 'package:flutter/material.dart';
import 'dart:ui' as ui;

import '../base/christmas_light_style.dart';

class ChristmasLightTabBar extends StatelessWidget {
  final TabController? controller;
  final List<Widget> tabs;
  final bool isScrollable;
  const ChristmasLightTabBar({super.key, required this.tabs, this.controller, this.isScrollable = false});

  @override
  Widget build(BuildContext context) {
    return TabBar(
      tabs: tabs,
      isScrollable: isScrollable,
      controller: controller,

      padding: EdgeInsets.symmetric(vertical: 20.0),
      indicator: CustomTabIndicator(
        gradientColors: [
          christmasLightStyle.gradientColors.first,
          christmasLightStyle.gradientColors[1],
        ]
      ),
    );
  }
}

class CustomTabIndicator extends Decoration {
  /// Create an underline style selected tab indicator.
  ///
  /// The [borderSide] and [insets] arguments must not be null.
  const CustomTabIndicator({
    this.borderSide = const BorderSide(width: 2.0, color: Colors.white),
    this.insets = EdgeInsets.zero,
    this.gradientColors = const [],
  }) : assert(borderSide != null),
       assert(insets != null);

  /// The color and weight of the horizontal line drawn below the selected tab.
  final BorderSide borderSide;

  /// Locates the selected tab's underline relative to the tab's boundary.
  ///
  /// The [TabBar.indicatorSize] property can be used to define the tab
  /// indicator's bounds in terms of its (centered) tab widget with
  /// [TabBarIndicatorSize.label], or the entire tab with
  /// [TabBarIndicatorSize.tab].
  final EdgeInsetsGeometry insets;

  final List<Color> gradientColors;

  @override
  Decoration? lerpFrom(Decoration? a, double t) {
    if (a is CustomTabIndicator) {
      return CustomTabIndicator(
        borderSide: BorderSide.lerp(a.borderSide, borderSide, t),
        insets: EdgeInsetsGeometry.lerp(a.insets, insets, t)!,
      );
    }
    return super.lerpFrom(a, t);
  }

  @override
  Decoration? lerpTo(Decoration? b, double t) {
    if (b is CustomTabIndicator) {
      return CustomTabIndicator(
        borderSide: BorderSide.lerp(borderSide, b.borderSide, t),
        insets: EdgeInsetsGeometry.lerp(insets, b.insets, t)!,
      );
    }
    return super.lerpTo(b, t);
  }

  @override
  BoxPainter createBoxPainter([ VoidCallback? onChanged ]) {
    return _UnderlinePainter(this, gradientColors, onChanged);
  }

  Rect _indicatorRectFor(Rect rect, TextDirection textDirection) {
    assert(rect != null);
    assert(textDirection != null);
    final Rect indicator = insets.resolve(textDirection).deflateRect(rect);
    return Rect.fromLTWH(
      indicator.left,
      indicator.bottom - borderSide.width,
      indicator.width,
      borderSide.width,
    );
  }

  @override
  Path getClipPath(Rect rect, TextDirection textDirection) {
    return Path()..addRect(_indicatorRectFor(rect, textDirection));
  }
}

class _UnderlinePainter extends BoxPainter {

  _UnderlinePainter(this.decoration, this.gradientColors, VoidCallback? onChanged)
    : assert(decoration != null),
      super(onChanged);

  final CustomTabIndicator decoration;
  final List<Color> gradientColors;

  @override
  void paint(Canvas canvas, Offset offset, ImageConfiguration configuration) {
    assert(configuration != null);
    assert(configuration.size != null);
    final Rect rect = offset & configuration.size!;
    final TextDirection textDirection = configuration.textDirection!;
    Rect indicator = decoration._indicatorRectFor(rect, textDirection).deflate(decoration.borderSide.width / 2.0);
    if (indicator.width > 20) {
      final center = indicator.center;
      indicator = Rect.fromLTRB(
        center.dx - 10,
        indicator.top,
        center.dx + 10,
        indicator.bottom,
      );
    }
    final Paint paint = decoration.borderSide.toPaint()..strokeCap = StrokeCap.square;
    if (gradientColors.isNotEmpty) {
      paint.shader = ui.Gradient.linear(indicator.topLeft, indicator.bottomRight, gradientColors);
    }
    canvas.drawLine(indicator.bottomLeft, indicator.bottomRight, paint);
  }
}
